Strength of fixation in non-metallic vs. metallic tension band wiring of patella fractures – A human cadaveric biomechanical study

Jonas Adjal*, Asger Haugaard*+, Liv Vesterby*, Huda Ibrahim Muhudin^, Kevser Sert^, Morten Grove Thomsen*, Peter Toft Tengberg*, Ilija Ban*, Søren Ohrt Nissen*+

* Department of Orthopaedic Surgery and Traumatology, Hvidovre Hospital, CORH, Denmark + Department of Orthopaedic Surgery and Traumatology, Køge Hospital, Sjællands Universitetshospital, Denmark ^ Danmarks Tekniske Universitet, DTU, Technical University of Denmark, MEK – Department of Mechanical Engineering, Denmark.

Background: Transverse patella fractures are traditionally treated with metallic tension band, which is associated with high reoperation rates due to implant failure, infection, and most of all implant prominence. Non-metallic techniques could be a viable alternative.

Aim: To assess whether strength of fixation of transverse patella fractures using a non- metallic all suture-based technique applied only in soft tissue is comparable to traditional metallic tension band.

Materials and Methods: Twenty paired human cadaveric specimens were included. A transverse fracture was created, reduced and fixated using either a standardized non-metallic or metallic technique in a pairwise random fashion. Metallic fixation was done according to the AO description of modified anterior tension band wiring with k-wires. Specimens were fixed in 90 degrees of flexion and underwent 200 cycles of loading in a MTS® apparatus by pulling the Quadriceps tendon to 300 Newton. Fracture displacement was optically monitored using digital image correlation. Primary outcome was mean fracture displacement after 200 cycles compared to the first cycle. Subsequently, loadto-failure was assessed by a monotonic pull to 1000 N. Failure was defined as a drop in the force measured by the force transducer.

Results: For cyclic loading analysis, one specimen from each group was excluded due to technical difficulties with the DIC. Median (min-max) fracture displacement was 0.65 mm (0.06-1.3) in the non-metallic group (p=0.931) and 0.68 mm (0-1.23) in the metallic group. No difference in displacement was found between the two groups in the repeated measures analysis of variance (p=0.5524). For load-to- failure analysis one specimen was excluded. 2/9 specimens failed in the non-metallic group (at 979 and 635 N) and 2/10 failed in the metallic group (745 and 654 N).

Interpretation / Conclusion: Non-metallic and metallic techniques showed similar strength of fixation during both cyclic and failure loading. We conclude that the non- metallic technique biomechanically is a viable alternative to traditional tension band fixation. Non-metallic techniques may have fewer implantrelated complications, which we suggest as a focus for future studies.

Local concentrations of gentamicin obtained by microdialysis after a controlled application of a GentaColl sponge in a porcine model

Maja Thomassen, Pelle Hanberg, Maiken Stilling, Klaus Petersen, Kjled Søballe,
Lasse Krag, Carsten Højskov, Mats Bue

Orthopaedic Research Unit, Aarhus University Hospital; Department of Orthopaedic Surgery, Horsens Regional Hospital; Department of Orthopaedic
Surgery, Aarhus University Hospital ; Institute of Clinical Medicine, Aarhus University Hospital; Department of Clinical Biochemistry, Aarhus University Hospital

Background: Local treatment with gentamicin may be an important tool in the prevention and treatment of surgical site infections in high- risk procedures and patients.

Purpose / Aim of Study: The aim of this study was to evaluate the pharmacokinetic profile of gentamicin in bone and surrounding tissue, released from a
controlled application of a GentaColl sponge in a porcine model.

Materials and Methods: In 8 female pigs, a GentaColl sponge of 10×10 cm (1.3 mg gentamicin/cm2) was placed in a cancellous bone cavity in the proximal tibia. Microdialysis was used for sampling of gentamicin concentrations over 48 hours from the cavity with the implanted GentaColl sponge, cancellous bone parallel to the cavity over and under the epiphyseal plate, cortical bone, the intramedullary canal, subcutaneous tissue, and the joint cavity of the knee. Venous blood samples were obtained as reference.

Findings / Results: The main finding was a mean peak drug concentration (95-CI) of gentamicin in the cancellous bone cavity containing the implanted
GentaColl sponge of 11,315 (9,049-13,581) µg/ml, persisting above 1000 µg/ml until approximately 40 hours after application. Moreover, the concentrations were low (< 1 µg/ml) in the surrounding tissues as well as in plasma.

Conclusions: The mean peak gentamicin concentration from the cancellous bone cavity after a controlled application of a GentaColl sponge was high and
may be adequate for the prevention of biofilm formation. However, high MIC strains and uncontrolled application of the GentaColl sponge may jeopardize this conclusion.

Suggestion for new pubofemoral distance cut-off value for instability in lateral position during DDH screening
Hans-Christen Husum, Michel Hellfritzsch, Nina Hardgrib, Bjarne Møller-Madsen, Ole Rahbek

Department of Orthopedics, Aalborg University Hospital; Department of Radiology, Aarhus University Hospital; Department of Pediatrics, Aarhus University Hospital; Department of Children’s Orthopedics, Aarhus University Hospital

Background: The current screening program for DDH in Denmark is insufficient in detecting all children with DDH. The Pubofemoral distance (PFD) has been proposed as a new, simple and inexpensive screening tool which could pave the way for a new cost-effective universal screening program for DDH in Denmark,

Purpose / Aim of Study: to validate pubo-femoral distance (PFD) as an indicator for instability of the hip in lateral position in Danish newborns screened for developmental dysplasia of the hip (DDH).

Materials and Methods: All participants had undergone ultrasonographic diagnostics using the modified Graf technique. In addi-tion, PFD measurements
in lateral position were performed. Results were compared between 25 infants who had been treated for DDH because of dysplastic appearance on ultrasound combined with instability and a control group consisting of 100 untreated infants screened for DDH. Sensitivity, specificity and cut-off points were determined using Receiver operating characteristics (ROC) analysis.

Findings / Results: We found a mean PFD of 6,83mm (6,2-7,4mm) in the treated group with the control group PFD of 3,44mm (3,3-3,6mm) (p <
0,005). A PFD value above a threshold of 4,4mm yielded a sensitivity of 100% and a speci-ficity of 93% for detecting instable DDH

Conclusions: PFD measured in lateral position was shown to be significantly increased in hips of children treated for DDH with Dennis Browne hip brace compared to healthy children with unaffected stable hips. Furthermore, the PFD measurement is characterized by a high level of sensitivity and specificity at a cut-off value of 4,4mm. A cut-off value of 6.00 mm has been previously reported as the gold standard in su-pine position. We suggest that 4.4 mm is used in lateral position.

Increased risk of revision in total knee arthroplasties following high tibial osteotomy is explained by patient demographics

Anders El-Galaly, Poul Torben Nielsen, Steen Lund Jensen, Andreas Kappel
Department of Orthopaedics Surgery, Aalborg University Hospital

Background: High tibial osteotomy (HTO) is used to treat primary osteoarthritis (OA) of the medial or lateral knee chamber in young active patients. The aim is to relief pain while preserving the knee joint thus postponing the need for arthroplasty. However, the influence of HTO on the survival of a subsequent total knee arthroplasty (TKA) is still debated.
Purpose / Aim of Study: We conducted this nation-wide registry study to evaluate the influence of HTO on the survival of TKA.
Materials and Methods: From the Danish Knee Arthroplasty Registry, we retrieved 1,049 TKA inserted from the 1st of January 1997 till the 31st of December 2015 in knees previously treated with HTO. We compared these with 63,954 de novo TKA without prior surgery. We analyzed demographics and calculated the estimated survival by Kaplan-Meier analyses and multi-variate Cox regression covering prior HTO, sex and age. In addition, we compared the indications of revision between the groups.
Findings / Results: The proportion of males were significantly higher in the prior-HTO group (57% vs 35%, p<0.001) and the patients were significantly younger at the time of TKA with a median age of 62 as opposed to 70 years (p<0.001). TKA inserted in knees previously treated with HTO had an inferior estimated survival (p<0.001) with a crude hazard ratio (HR) of 1.70 (95% CI: 1.38-2.10, p<0.001). However, after adjustment for the differences in sex and age the two groups had a similar risk of revision with an adjusted HR of 1.17 (95% CI: 0.96-1.42, p=0.11). Instability showed a trait of been more frequent in the prior-HTO group (25% vs 18%).
Conclusions: In this nation-wide registry study TKA following HTO were revised more often than de novo TKA. However, our analyses suggest that the increased risk of revision is due to younger age and increased percentage of males in this group rather than the prior HTO.

Closed Reduction of Distal Radius Fractures: A Systematic Review and Meta-analysis

Hjalte Würtz, Sükriye Corap, Julie Erichsen, Bjarke Viberg
Department of Clinical Research, University of Southern Denmark; Department of Orthopaedic Surgery and Traumatology, Hospital of South West Jutland; Department of Orthopaedic Surgery and Traumatology, Kolding Hospital; Department of Orthopaedic Surgery and Traumatology, Odense University Hospital

Background: To date, there has been insufficient evidence to determine the best possible method of closed reduction for distal radial fractures (DRF).
Purpose / Aim of Study: To compare reduction of DRF by finger-trap traction (FTT) with manual traction (MT) in terms of radiographic outcome and pain in RCTs.
Materials and Methods: Pubmed, Embase and Cochrane databases were searched on March 1st 2016. Two authors independently screened 4348 articles by title and abstract. 14 articles were reviewed full-text. Bias was assessed by the Cochrane Risk of Bias Tool. Meta-analysis was performed for radial shortening and dorsal tilt while it was not possible for pain assessment due to different outcome measures.
Findings / Results: 3 RCTs with a total of 483 patients were included, 240 FTT and 243 MT. Risk of bias was generally unclear. None of the studies reported any statistically or clinically significant differences in radiographic outcome. Forest plot of the dorsal tilt showed 0.43[0.25;0.61, p<0.00001] in favor of MT. Radial shortening forest plot showed -0.19[-0.37;-0.01, p=0.04] in favor of FTT. One study found FTT associated with less pain, even without anesthesia, and another found FTT to be associated with a better functional outcome.
Conclusions: FTT seems to be slightly superior in restoring radial length compared to MT whereas MT seems sligthly superior in restoring dorsal tilt compared to FTT. FTT might be less painful. The studies were very heterogenic and further studies are warranted.

Radiographic cup position following posterior and modified direct lateral approach in total hip arthroplasty. An explorative randomized controlled trial with 80 patients.

Christine Kruse, Signe Rosenlund, Leif Broeng, Søren Overgaard.
Department of Orthopedic Surgery and Traumatology, Odense University Hospital, Institute of Clinical Research, University of Southern Denmark, Denmark

Background: The two most common surgical approaches for total hip arthroplasty (THA) are the posterior and lateral approach. Differences in cup placement may contribute to differences in clinical outcomes between the two approaches. Improper placement of the cup can cause dislocation and reduced hip abductor strength.
Purpose / Aim of Study: The aim of this study was to compare cup position in the two approaches. A secondary aim was to compare changes in femoral offset (FO), cup offset (CO), total offset (TO) and abductor moment arm (AM), and to evaluate intra- and interobserver reliability of the methods used.
Materials and Methods: In a randomized controlled trial, 80 patients diagnosed with primary hip osteoarthritis scheduled for THA were assigned to operation with posterior or modified direct lateral approach. 38 patients were included in each group for the measurement cup position. FO, CO, TO and AM were measured on pre- and postoperative radiographs in 28 patients in each group. Unpaired t-tests were used to evaluate differences between the groups. An ICC value of ≥0.81 was considered excellent strength of agreement.
Findings / Results: In the posterior group, anteversion was 4.8� larger than in the lateral group (p=0.006) but inclination was 4.9� less steep (p<0.001). A larger FO of 4.3mm (p=0.006), TO of 6.3mm (p<0.001) and AM of 4.8mm (p=0.001) was found in the posterior group. There was no significant difference in CO (p=0.08). Intra- and interobserver reliability were excellent for all measurements (ICC 0.93-1.00).
Conclusions: We found a statistically significant difference in cup position between the two approaches. Femoral offset and abductor moment arm were restored after THA using the lateral approach but significantly increased when using the posterior approach.

Significant role on rotatory stability of the anterolateral ligament in ACL insufficient knees

Mette Tavlo, Salameh Eljaja, Jørgen Tranum-Jensen, Volkert Siersma, Michael Rindom Krogsgaard
Institut for Cellulær og Molekylær Medicin, Københavns Universitet; Afdeling for Idrætskirurgi, Bispebjerg Hospital; Forskningsenheden for Almen Praksis, Center for Sundhed og Samfund

Background: Recent studies have described the anatomy of an anterolateral ligament (ALL) of the knee. This ligament has been linked to the Segond fracture that is patognomonic for tear of the anterior cruciate ligament (ACL). ALL is hypothesised to be important for the internal rotatory stability of the knee, but its mechanical effect has yet to be clarified.
Purpose / Aim of Study: Our aim was to test the function of the ALL for rotatory and anterior-posterior (AP) stability in ACL insufficient and reconstructed knees and the effect of anatomical ALL reconstruction with a tendon.
Materials and Methods: In 18 cadaver legs ALL was dissected. Function of ALL (+/- ALL) and of ALL reconstruction (reALL) was tested with the ACL removed (-ACL) and reconstructed (+ACL) with following combinations: +ACL-ALL, +ACL+ALL, – ACL+ALL, -ACL-ALL, -ACL+reALL and +ACL+re-ALL. All combinations were tested with the knees in 0, 30, 60 and 90 degrees of flexion. AP stability was tested with a Rolimeter. Rotation of tibia was applied with 50 N internal and external and measured photographically from K-wires inserted in tibia and femur.
Findings / Results: The ALL did not appear uniform, but was well defined in 78 %. ACL (+/-) had a significant effect on the AP stability but not on rotation. ALL (+/-) had significant effect on the rotatory stability (p = 0.0006), regardless of the condition of ACL, and on the AP stability in ACL insufficient knees (p = 0.023). The lost stability of ALL was regained when ALL was reconstructed.
Conclusions: ALL is a major rotational stabilizer. If ALL is torn in connection with ACL rupture, reconstruction of ACL is not re-establishing rotatory stability. When ALL is reconstructed anatomically, rotatory instability is re- established. ALL reconstruction as supplement to ACL reconstruction might be considered in patients with a Segond fracture.

No association between serum metal-ions and implant fixation in large-head metal-metal THA. A 5 year RSA study.

Mette Holm Hjorth, Kjeld Søballe, Stig Storgaard Jakobsen, Nina D Lorenzen, Inger Mechlenburg, Maiken Stilling
Ortopædkirurgisk Aarhus Universitetshospital

Background: The failure mechanism of metal-metal(MoM) total hip arthroplasty(THA) has been related to metal wear-debris and pseudotumor, but it is unknown if implant fixation is affected by metal wear-debris.
Purpose / Aim of Study: Study if the fixation of large-head (LH) MoM THA is affected by the metal wear-debris
Materials and Methods: 41 patients (31 male) at a mean age of 47 (23-63) years with a total of 49 MoM THA were followed with radiostereometric analysis post-operative and at 1, 2 and 5 years for analysis of implant migration. They also participated in a 5-7 year follow-up with measurement of serum metal-ions, questionnaires (Oxford Hip Score(OHS) and Harris Hip Score(HHS), measurement of cup and stem position and periprosthetic BMD
Findings / Results: Between 1-2 years Total Translation (TT) was mean 0.04 mm (95% CI: -0.07-0.14) (p=0.49) for the stems and between 2-5 years TT was mean 0.13 mm (95% CI: -0.25; -0.01) which was significant (p=0.03) but within the precision limit of the method. Between 1-2 and 2-5 years there was no significant TT or total rotation for the cups. We found a dichotomized migration pattern of TT between 2-5 years, where 6 cups and 6 stems had migrations above the precision limit of the method (2 pt. had both cup and stem migrations above precision limits).A positive association between total OHS <40 (n=4) and cup migration (p=0.04) was found, but no significant associations between cup or stem migration and female gender, stem and cup position, T scores <-1 or metal-ion levels>7ug/l.
Conclusions: Between 2-5 years, 6 cups and 6 stems had migrated above the precision limits of the method, but patients were asymptomatic and serum ion levels were <7ug/l. The remaining cups and stems were well-fixed between 1- 5 years. Seemingly, metal wear-debris does not influence fixation of hip components in LH MoM THA at midterm follow-up.

Should the knife be discarded after skin incision in arthroplasty surgery?

Casper Ottesen, Annette Skovby, Henrik Husted, Alice Friis-Møller, Anders Troelsen
Dept. Of Orthopaedic Surgery and Dept. of Clinical Microbiology, Hvidovre University Hospital